The Olympics: Does it actually help the economy of the host countries?

Pyeongchang, South Korea will host 2018 Winter Olympics

          
On July 7^th, South Korea won to host 2018 Winter Olympics. South Korea calculates to gain 27billion dollars by hosting the Olympics. Also, the potential economical benefit of the Olympics is estimated as twice as large as the benefit of the 2002 Korea-Japan World Cup and 4 times lager than 1988 Seoul Olympics. As South Korea, a lot of countries try to host the Olympics to boost their economics. However, it is hard to say the Olympics always bring economical benefit to the host countries.